TLDR - Basically you're giving them the blue pill in the matrix, they think their channel is doing good, getting 126 hours of watch time a week when really there one person away from 0 hours. You really shouldn't do this, it most likely won't actually help.
The Long -
You shouldn't be trying to inflate their views. It will never actually impact their video that much anyway. Youtube mainly focuses on trending, by which I mean if they get 100 hours of watch time in the first 60 min of the video being posted Youtube will notice and push that to more people, but 100 hours over 1-2 weeks and youtube doesn't really care.
If I set the playback speed to 2x, would that effectively double the amount of watch time her channel gets?
Actually, certified Youtube Experts have shown that Youtube at 2x speed counts as 1/2 the watch time. Watch time, is the amount of time you spend watching the video. Basically, if the video was running for 1 hour, then it's 1 hour watch time, doesn't matter if it was 1x 2x 0.5x 0.25x
Inflating view count could lead to a channel's termination,
true but most likely not if the creator isn't found to be the source of the "inflation". Youtube mentioned (I wish I could find this interview) it's hard to do that, especially with large channels because "haters" and trolls and competitors would just buy them a lot of fake views so youtube would delete their channel. But you're not wrong. It waaaay more likely to get deleted if it's a small channel like the OP mentioned.
I SUSPECT that watch time is calculated on only one watch through per viewer.
1 - This would be really bad for music channels that are filled with listeners repeating it all day. I have songs I literally listen to all day. I'd like to imagine that Youtube knows if its a music channel and values it basics on that. But then again, when I was a kid.... I rewatched game trailers over and over again to try to find out what was happening in it.
2 -If that is true, do you think it's also true for views? If so, 1 video has 6 billion views... I doubt 6 out of 7 humans or youtube accounts watched it once. Far more likely that a large few (I know it's an oxymoron) watched it several time.
If that was considered false views, why do they give us the tools to do so.
This is 100% false views though... the OP mentioned running videos in the background with the audio turned off to inflate their views. They don't give you tools to inflate views. Personally (I never tested this) but I think youtube knows when it's in the background and when the column of the player is set to mute. Like others have said youtube isn't stupid plus they use AI for this.
"Trying to intentionally increase views is a waste of time. YouTube eliminates unwanted views from the same place and repeats views in a short time."
I've been told that youtube caps your to like 8 views per single video per undisclosed amount of time. maybe per day. maybe per few hours idk. I got this info from people who managed large channels BUT I haven't talked to them about youtube since like 2016 so I'm sure things have changed. That being said, the OP mentioned using a playlist not just a single video.... so it might be more likely to count as a view? idk.
To be fair, my facts are probably all outdated. Also, Youtube certified experts don't actually work for Youtube and they are basically just making an educated guess on how the system works based on research on their clients' channels. All that to say, who knows how accurate my intel was to begin with.
cause I'm too lazy to try and error something new, unless it is recommended by the person I trust. Well, you know guy......